How to (voltage drop) test a starter motor circuit

[@davidscott1340]

I am a certified mechanic and was looking for a how to video cause I was tired of typing of typing out the explanation on social media. Sharing this video will save me a lot of time. Thank you.

[@thomasldeanjr3337]

This is one of the best explanations of voltage drop in a starting system I've seen. Thank you so much!

[@KamoheloPotsane]

Been watching other videos about voltage drop in a starter motor circuit and could understand jack! Here I am bumping into this well detailed and excellently demonstrated video by Mr. Miller, now I feel like an A+ student lol, thanks Mr. Miller, in the morning I'm definately going to check my car and try to diagnose where I could be losing voltage. Thanks a lot!

[@JustinMillerAutomotive]

Thanks for the feedback! I am glad it helped you. Good luck with the car.

[@milotorres6894]

Teaching not easy same sentiments automations workings can become fickled fiasco basics fuel fire ,and air needs eases rundown electrical most important...

[@mystic24100]

This is a very good explanation, wish I would have saw it 6 months ago. I like (not really) the ones that sometimes it works and sometimes not? Had the neighbors lawn mower that would not crank, no click, nothing. Bypass the switch and it worked. Never saw this before, but put in a new switch and it works every time. He comes over to pick it up and does not work!! Turn the switch on a couple more times and it works like a champ. He has used this summer, sometimes, he does have another mower. With all the safety switches there are a lot of connections to check, but once you understand the system you can find the problem.

[@sandiegorestorations877]

Thank you for this video - I’ve watched about 10-15 different videos on this and this one was the most clear! You’ve helped me diagnose the issue with my project car!

[@beanercanned9021]

Hey my car has the same problem s wire only draws 0.2 volts

[@kville5796]

This is just up my street; very detailed and informative. Justin you're a star.

[@dortiz_dk3443]

Very educational for us getting ready for the A1 ASE Test! Thank you so much for making this video!

[@stocks4bt]

Every teacher should use a setup like this one. Visual teaching & theory is better than just teaching theory

[@ndigs]

Especially when your dealing with AUTOMOTIVE issues...

[@milotorres6894]

Troubleshooting made simple explanation helps clear the air a b c no confusion spot on same page concepts...

[@brediaable]

I have had a lot of trouble understanding voltage drop concept it was really troublesom for me I have been to just about every web site there is well maybe not everey one but this guy (justin miller) is the best teacher, BEST VIDEO , best explanation, of voltage drop that there is on the web and his simulator might be the reason why I don,t know but after watching his you tube video a few times I thoroughly understand voltage drop which I thought I did before but I was mistaken. This guy is a BAD ASS TEACHER I don,t care hats off to you JUSTIN MILLER THANKS A LOT

[@Querencias7]

E X C E L L E N T demo, very nice setup too. Nice job indeed. Sharing your knowledge is greatly appreciated.

[@hydrationtekirrigation1451]

thank you for the light in the darkness! now I know how to use ohm readings not just for zero resistance but for voltage loss, and I understand the circuit! nice.

[@JustinMillerAutomotive]

Glad it was helpful!

[@radfourrunner8840]

Hi Justin, Thanks for this Excellent Setup and Presentation. Love your channel! One observation however... The starter relay (black module) is there so the ignition switch would not have to carry the current necessary to energize the starter solenoid (I measured 12 amps on my Toyota 4Runner). The starter relay is added to the system, so the ignition switch "start" contacts will only have to carry the low current needed to energize the starter Relay while the Relay contacts will carry the higher current needed to energize the starter solenoid (12 amps on my 1986 Toyota 4Runner). However, on your circuit the starter relay load supply is still taken from the ignition switch. This means that when ignition switch is in "start" position the current passing through the ignition switch "start" contact is: Low current to energize the starter Relay coil PLUS the approx. 12 amps needed to energize the starter Solenoid. This defeats the purpose of having the starter relay. This oversight is the cause of cranking problems on many first-generation Toyota 4Runners, and possibly other vehicles as well. Cheers! :)

[@tubetime39]

I was wondering about that relay and what it's purpose was. The relay doesn't carry the current to the starter Solenoid though,..eh? The wire from the relay carry's to the solenoid carries the current. Too bad he couldn't find where the problem was. He didn't explain that fuse or whatever between the pos batt cable going to the starter. Hmm. Confusing. Didn't explain touching meter from pos to pos either. Not the place for me to start learning car electrical. Bummer. i suppose I'll have to go through a lot more video's. Whew I wish one channel would go through from one step to the next. I can't even find a good book on it.

[@tubetime39]

PS, Nice board though 😊

[@billm5758]

Great video in telling you how to pinpoint the drop, not just a description of how it is occurring!

[@brentonpacker3291]

This is an amazing video. You must be an engineer. I love engineers!

[@philgray1023]

If I had seen this during my apprenticeship I would not have become a nurse.

[@اللهمصلعلىمحمدوالمحمد-ص8ت]

Why

[@jameswhitbread7173]

But your saving life's so perhaps that was your true calling. Anyway it's all going electric soon

[@davidfrench3657]

At least you don't have to buy tools to do your job now

[@matthewdubois6792]

@@jameswhitbread7173more likely getting turkey sandwiches and ginger ale while watching heart monitors.

[@871jamie]

You’re better off, being an auto tech you will eat a lot of bologna during the slow times.

[@labradormcgraw]

Neat mock-up. Makes it really easy to understand.

[@drjimjam1112]

Love the way this is made so simple. 4 places to check for voltage drop in the starter circuit.

[@mikeamidi522]

Really Really wonderful demonstration. I really liked this demo.

[@funnyture]

most and best lesson I had from you tube. thanks for efforts sir.

[@ifixeditmyself1926]

This was very helpful. I'm trying to figure out the click coming from my 99 Buick century at the solenoid on the starter and this helped me to understand the starter motor a lot better. Excellent!

[@acampbell198]

Great video, first time I am learning about voltage drop testing...love that!

[@todddra]

Great video. I'd like to see the troubleshooting continue to find the exact problem!

[@MagicNomadic]

was thinking the same thing, 2 years after your comment.....lol.

[@pablogomez7519]

same here because that's my problem 🙄 I turn the key to the run position and no power on the wire to the S terminal

[@CWellman9345]

Best explanation I have found! Great Job

[@gustavogarcia8214]

this is a very good. explanation about how the starter work and the possible problem we can have with.and how to check it

[@AnithRamkissoon]

Good diagnosis. Best explained.👍💯

[@benjamin-rw8qm]

best explanation I found online! thank you very much!

[@Matthew-jr1xr]

Awesome video...saved me from buying a new battery.

[@billsmith2212]

You did test between the battery POST and TERMINAL . Always try to go directly on the post if possible or be sure there isn't an excessive drop there . Always go directly on a starter battery post or solenoid post and not a tab or nut . There could be corrosion there . Great lesson .

[@christopherhuffer8925]

Trying to diagnose my 62 Impala. This video was really helpful!

[@davidm3210]

Great video, thank you, If I'm not mistaken the first test determines if sufficient amperage is being delivered by the battery (when under load, of course). I seem to recall from Chris Fixx that a dip down to app. 9V (between battery terminals) is acceptable when cranking.

[@JustinMillerAutomotive]

That is correct. As a rule of thumb, when using a multimeter with min/max function, the voltage should not go below 9.6 volts during cranking. If using a lab scope, it should not go below 8.0 volts (because lab scopes are faster and capture the real minimum voltage).

[@tommyboyou812100]

@@JustinMillerAutomotive pop pop on

[@blisteredthumbsdeas]

Great vid. Clean, precise and most importantly correct

[@sandyande]

Explained well, many thanks, sandy

[@waiting4aliens]

Thank you. Very clear, and reinforced other knowledge gained.

[@MMGJ10]

Awesome video. This explains everything perfectly. Thank you!

[@slugg6632]

Thank you for this clear video can’t wait to troubleshoot my sisters car

[@1977np]

Good beginner basics troubleshooting video. In some episode maybe you could outline starter problems specifically if all those 4 measurements are ok. Thx

[@mannyvalero3250]

Omg 🤯 it makes sense now. I can't thank you enough....😭

[@megamac3898]

Thank you very much for the clear Info I have spent ages on web to understand it till I saw ur videos , greetings from Egypt .

[@nealk6387]

Buy a esi starter buddy. This tool has saved me a ton of time.

[@WTFisupDennys]

Frick this is seriously the best video!

[@jorgecabrera2589]

Excellent 👍 video , instructional, Sr,you teaching in school, you excellent how teaching, so good

[@spelunkerd]

The main assumption you make when you use a device to put a load on a wire is that the device is drawing current. At 7:43, there wasn't enough energy flowing to fully close the solenoid contacts, so the main source of moving electrons comes through the relay to the S post, not through the big B+ wire. With no current on the B+wire, you haven't yet proven that wire is good, it was a failed drop test. On the other hand, if that wire was the problem we expect to see a drop. I really like your four step method, it's a way to quickly screen for wiring issues and get the job done without making a critical error. Doing it with a test light is a little faster but stands a chance of missing a problem because the light fails to detect an issue.

[@JustinMillerAutomotive]

You are right. In some cases, you may be trying to diagnose a starting system in which the starter isn't activating. While you will not be able to load the circuit without a working starter motor, you can still perform these steps to determine what the cause of the problem is. If the voltage is not dropping in the wires (even if the starter is not spinning), you can know that the wires are not the cause of the problem. Likewise, you can measure the voltage at the battery while attempting to crank the engine. Even if the starter does not spin, if the battery voltage remains high, then you can know that the battery is not the cause of the problem. It is true that you have not load tested the battery, but you can know that it is not the reason the starter is not turning on. You can load test it later, once you have found the problem with the starting system.

[@spelunkerd]

@@JustinMillerAutomotive This is first class teaching. One of the things that surprises me is how often working professionals mess this up. As much as thinking it through carefully is important, those guys need a streamlined four step check list approach, much like airline pilots use a checklist every time they get into a plane. Something that can be memorized, for a task done every day. Conventional teaching fails them because it isn't fast, there are too many options, too much thinking! ScannerDanner uses an easy four step test light algorithm, which gets a correct diagnosis about 90% of the time. The weakness is the insensitivity of the test light, especially for the final ground test.

[@nickayivor8432]

Good Evening Justin Miller take care and have a great day Justin Miller God bless you Justin Miller Great tutorial ❤ IT 👍 From Nick Ayivor from London England UK 🇬🇧

[@aeriksh6873]

These Are the details I was looking for! Awesome and thanks

[@JoseGonzalas]

Excellent explanation. 10/10.

[@kennidyulin2565]

Great video thanks for your knowledge

[@zeroalcohol]

Very good explanation. Thanks for sharing.

[@EdWard-ji2hj]

Super useful and easy to understand. Thanks

[@milotorres6894]

Good explain techniques must've had a excellent teacher or degree or self taught either way much thanks for clearing the air had starer issues this helped the best by far good Man...

[@milotorres6894]

Spell check sucks .

[@leonking9459]

wish we have this in our school, students will learn a lot more than written visual aids.

[@superfluteman1]

Doesn't get better than this. Thanks

[@joelarbo3425]

This was an awesome teaching video!

[@mengluo4287]

wa, mind blowing! Best video on starter circuit on KZbin!

[@beefcakes27]

Excellent video, Justin..!

[@alexander0194]

Thank you for this video. Immensely helpful.

[@tuanas458]

Damn. That was mad good educational. Thanks my mans.

[@oriancunningham]

great presentation, highly informative

[@nathandoering9115]

Hello Justin. I need to start off with saying this was a great video. Very informative. I was wondering if you could show the back side of the test station, how the faults are introduced, and what was used to create the faults. I would like to build this test station. Thank you!

[@Micscience]

I am a little confused when you did the (S) terminal test for the solenoid I think what you meant to say is you are missing like 2 volts and not 11 volts because the reading was 11 volts. Sorry I was just trying to make sense of what you are saying. By far you are the best at simplifying all this voltage drop so thanks for sharing.

[@JustinMillerAutomotive]

You are correct. I am not sure what I said, but that is definitely what I meant! There were about 2 volts missing at the "S" terminal compared to the positive battery terminal, which means that that those 2 volts are being dropped through some unwanted resistance somewhere between the battery and the "S" terminal.

[@hoanggia2222]

@@JustinMillerAutomotive Excuse me, I think that what you said in the video is right. You are missing 11,2 volts because the DVOM showed voltage between positive post(13,2 volts on the video) and "S" terminal, not the voltage at the "S" terminal. And the voltage at the "S" terminal is just about 2 volts compared to the negative post.

[@matssigm]

Thank you for a very good teaching. But i dont understand why the circuit still should read 12 volts when its closed ?

[@j.m.5995]

I like to place the ground wire on the actual case of the alternator to one of the mounting holes. That way it is primarily grounding itself thru that wire and not having to ground itself thru the block and anything that's grounded thru there. I avoid issues with magnetizing anything sensitive via the large inrush of initial current flow when you crank the engine

[@creme757]

Excellent information, very helpful! BUT modern cars have Immobilizers which makes things quite a bit more complicating. Especially in European models

[@JustinMillerAutomotive]

Yes. The purpose of this procedure is to help you identify which branch of the circuit the problem is in. From there, you would need to do pinpoint tests to find out exactly what the cause is. These tests still work on modern cars with immobilizer systems. If you find that you are not getting the proper voltage to the "S" terminal, you would need to refer to a wiring diagram and determine how to narrow it down further. Often, a scan tool may will helpful.

[@donaldlucas8688]

Very cool setup. Well thought out!

[@jimbodee4043]

Great visual illustration of diagnosis

[@seshachary5580]

very educative. Thank you regards

[@guitarplayerwannabee]

Fantastic tutorial. Many thanks

[@marvinhoodith7110]

Very great demo keep it up bro looking out for more.

[@timreeves3321]

HI Justin, great video! I'm hoping to make a board similar to yours for my high school auto class, and was wondering if you could give me some info on how you setup the back of the board?

[@jameslancaster8391]

Thank you for a great demonstration.

[@871jamie]

My voltage drop issue on my 93 Z28 turned out to be in the starter itself. But turned out to be two bad starters. Had me scratching my head a while because two different starters had the exact same issue. Sometimes they worked and sometimes they just clicked. Off the car they worked fine but put them under a load and both did the same thing. Finally installed a remote starter to the starter with it in the car and had the same issue as using the ignition key. Bought an expensive starter and that fixed it.

[@JustinMillerAutomotive]

Starters come in all quality levels! I always recommend buying "100% new" starters, never remanufactured.

[@summerrain3403]

This helped a lot, thank you for making this video.

[@annumlaz]

Excellent video to the point and easy to understand. Now, let's say the circuit components to the starter passed the voltage drop test, battery, battery positive, battery negative (ground), starter positive and solenoid positive(power). The solenoid grounds internally and provides power to the starter but the stater does not come on. Can you now do a voltage drop test on the starter to see if it has excessive internal resistance , missing volts, causing the starter's failed operation. Where would you put the leads of the DVOM on the starter and how would the readings look on the DVOM pass and fail?

[@JustinMillerAutomotive]

If you measure the voltage drop directly between the "M" terminal and the motor housing, you are measuring the voltage directly available to the motor. If your voltage is above about 9.6 volts, but the motor is not spinning, you have a problem with your motor. Most likely, the brushes are worn and need to be replaced, but it could also be an open or short in the armature windings.

[@iemandjwzz4614]

Absolutly great video!

[@nickayivor8432]

What do you call INTELLECTUAL AND PRODIGY and SUBSTANTIAL add one more KNOWLEDGEABLE the answer is Justin Miller My teacher Thank you very helpful information video 👌 👍 Take care and have a great day PRODIGY Justin Miller From Nick Ayivor from London England UK 🇬🇧

[@iriejam2164]

Excellent video! Concise, thorough. Could you say where I can get some teaching aids to purchase for my school?

[@peterjuhasz5143]

Excellent vid, thank You very much!

[@fabianemendez5172]

Good video... but Be nice if show the screen of the multimeter while cranking

[@liraziyad5806]

Thank you. very simple and clear.

[@flightofthefatman]

Thanks for the up...really great demonstration.

[@donaldlucas8688]

You should do a video of how you made this setup.

[@teabreak4t]

excellent trouble shooting guide

[@abcardenas35]

Thanks bro 🙏 🙌 💯

[@jdhappy7663]

If you're getting the resistance say from negative terminal to the starter housing that mean there's a bad ground somewhere

[@BarlitosC]

Now to play around for 8 more hours seeing if it is an actual ground problem or the starter housing is just so corroded I can’t get a good read!!!

[@jerryrobinson958]

This was a very good video

[@vicky-nc3to]

Porsche cayenne(tiptronic transmission) starts with ignition on + brake pedal pressed, so sometime if the engine starts without pressing brake, than is it the same problem of some safety switch in brake pedal as it is in clutch safety switch.... possibly short ?

[@DeLarryfication]

Please, do a simulation of a car alarm system whereby when the alarm is not disengaged then the car will not start. It would be pretty neat if you use the current circuit to add an alarm system.

[@evo6swap]

Thank you awesome information

[@girlcanic]

What did you isolate to cause this problem?

[@rem6792]

Phenomenal video man

[@paultomasi4619]

Excellent! Very clear

[@subatomicparticle6535]

At about 9:00 of the video the very last test being performed of the "S" terminal at the Solenoid. The multimeter is hooked up to the "S" terminal and to the battery and the author says "And right now I read battery voltage"?? I'm confused as to how you can be reading battery voltage at terminal "S" without the key being turned to the start position. If there's battery voltage at the "S" terminal with the key only in the on position and not in the start position then wouldn't the solenoid be activated turning the starter motor.

[@JustinMillerAutomotive]

It is because the other lead is on the positive battery terminal. The battery terminal has 12 volts, and the S-terminal is connected to ground through the solenoid windings. Keep in mind that a voltmeter measures a difference in voltage between the two leads. Once the solenoid circuit is complete, the S-terminal will then have 12 volts, which means that there should be almost no difference in voltage between the two leads and the meter will read close to zero. Does that make sense?

[@subatomicparticle6535]

@@JustinMillerAutomotive Thanks, my bad. I should have been watching the video more carefully as to where you were hooking up the multimeter leads and as you correctly point out the multimeter is reading battery voltage finding ground through the coil of the solenoid and once the circuit is activated are measuring the voltage drop from the battery positive terminal to the "S" terminal which should read close to "0" provided there's no resistance in the wires/connections creating a voltage drop, got it!

[@lucasgambino7162]

Great video! I followed everything with my toyota 22re pickup. It wont start or even attempt to, no click no sound nothing. Unfortunately i passed every test you did. That surprised me. So now im really confused on why it wont start! where do i go from here?

[@marinmotorsports]

I really want to understand this. In the case of a seized starter motor..if I connect to Battery + and the 'delivery' post on the starter motor, during activation,(and presuming the path is clean) I am expecting to see ALMOST no voltage drop, as, I am 'tapping in' before the suspected load, correct? I could instantly call out the motor in this case? (and now that I'm thinking about it, a bad ground path may play a role) Thank you, your video is great!

[@JustinMillerAutomotive]

Yes. That is correct.

[@jacklassley8002]

You said the small lead to the solonoid went all the way around all the other stuff,(ignition, relay etc.) then when it became a problem, you said you can check for the voltage loss at all the points you just said that wire bypasses?? It comes from a hole in your board, and winds up at the battery, but what is its actual path, and how many stops along the way is there ? I believe that is where my problem is. Only part I haven’t replaced is the nuetral trans switch (98 E350 V10) the wire alters direction beneath motor, not going where main power goes, but unless I tear the whole harness apart, I can’t find where it separates and where it comes from and what is in between. Costing me a fortune on parts, and not working since it’s my work truck. Will my starter still click if neutral switch is bad ?

[@JustinMillerAutomotive]

Your starter will not click if your neutral safety switch is bad. The neutral safety switch is required in order to get voltage to the small "s" terminal on your solenoid. If the solenoid is clicking, you likely need to check the voltage at the "B" terminal, on the ground, and on the "M" terminal to determine if the problem is in a battery cable, the solenoid, or the starter motor.

[@johnnylrico]

What messes me up is Why is there battery voltage from the switch on the solenoid and positive terminal with everything off when there shouldn't be a ground?Why would that switch be grounded when the ignition is off?

[@markferraro5250]

Great video Justin thank you

[@thugerrish]

Thumbs up for making that thing

[@ericscaillet2232]

The voltage did not drop much when he cranked the starter motor as there is no load on it,it would drop a bit more if it was installed

[@ifachner]

Great video, I'm trying to diagnose similar issues on a motorcycle. Any pointers? There is no relay not sure if the solenoid is grounded and the solenoid is separate.

[@gasousman]

Wonderful vid. Thanks so much.